Arrangement in electric induction furnaces without a closed ferromagnetic circuit



LuaLwre Dreyfus INVENTOR ATTORNEY.

NOV. 14, 1933. DREYFUS ARRANGEMENT IN ELECTRIC INDUCTION FURNACES WITHOUT A CLOSED FERROMAGNETIC CIRCUIT Filed Aug. 29, 1952 Patented Nov. 14, 1933 ARRANGEMENT IN ELECTRIC INDUCTION FURNACES WITHOUT A CLOSED FERRO- MAGNETIC CIRCUIT Ludwig Dreyfus, Vasteras, Sweden, assignor to Allmnna Svenska Elektriska Aktiebolaget, Vastera-s, Sweden, a corporation of Sweden Application August 29, 1932, Serial No. 630,801, and in Sweden August i), 1931 2 Claims.

In electric highi^requency induction furnaces without iron cores it has previously been proposed to insert ferro-magnetic parts between certain conductors of the winding in order to aiect the magnetic leakage and thereby reduce the eddy current losses in the winding. lt has now been found that such parts, ii inserted between the conductors of a winding provided with a ferro-magnetic shell highly contribute to an increase of the active magnetic flux, at the same time as its reducing action on the eddy current losses is considerably strengthened. The present invention therefore comprises the combination, in electrical induction furnaces without iron cores of a ferromagnetic shell surrounding the winding and ferromagnetic parts inserted between the separate conductors of the said Winding.

One form of the invention is illustrated in the accompanying` drawing, which shows one quarter of a furnace with a cylindrical winding in a vertical sectional view.

1 is the crucible, 2 the winding, 3 the magnetic shell and 4 the ferro-magnetic intermediary parts which preferably are laminated perpendicularly to the shell and have increasing number of laminations towards the ends of said shell. The axis of the furnace is indicated by a vertical dash and dotted line and a horizontal plane through the centre of the winding, about which it is assumed to be symmetrically arranged, by a horizontal dash and dotted line. Lines of magnetic flux are indicated by dotted lines, which show how practically all that ilui` which does not pass through the portion of the shell projecting towards the furnace is conducted G@ through the intermediary parts, which therefore considerably contribute to an increase of the active flux in the furnace, at the saine time as they reduce the axial leakage and thereby the copper losses in a more efficient degree than @5 hitherto known.

l claim as my inventionzl. In electrical induction furnaces, a receptacle for the material treated, a winding surrounding said receptacle, a ferromagnetic shell surrounding said winding and leaving the interior of said receptacle substantialiy free, and ferromagnetic sheets substantially perpendicular 'to said shell inserted between different turns of the winding carrying the same current.

2. In electrical induction furnaces, a receptacle for the material treated, a winding surrounding said receptacle, a ferromagnetic shell surrounding said winding and leaving the interior of said receptacle substantially free, and ferromagnetic parts laminated substantially perpendicularly to the shell inserted between difk ferent turns of the winding carrying the same current, the number of laminations increasing towards the ends of saidvshell.

LUDWIG DREYFUS. 

